'The bodies were found later'

The years leading up to 2007 in Ciudad Juarez, home to just over a million people, saw about 200 to 300 homicides a year, a normal amount, Molly Molloy, a professor and librarian at New Mexico State University, told Business Insider in December.

The next year, however, saw a more than fivefold increase, to over 1,600 homicides. That was followed by a jump to more than 2,500 killings in 2009. The bloodshed surged against in 2010, reaching over 3,500 slayings.

The next two years saw declines — to about 2,000 and then about 800, respectively — but the spike in homicides and the response to it disrupted life there.

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Ciudad Juarez Mexico killing violence drug war cartels

REUTERS/Alejandro Bringas

"The surge in killings was so bad ... I would find the mayor, oftentimes, spending part of the day praying for a miracle. The military was brought in, a move that many human rights activists to this day say made the violence even worse," Alfredo Corchado, a Dallas Morning News contributor and author, said during a panel discussion at the Wilson Center in Washington, DC, in early February.

The deployment of troops and federal police to Juarez was part of a larger shift undertaken in the late 2000s by then-President Felipe Calderon, who emphasized attacking urban trafficking points rather than rural production hubs. This militarization of the anti-drug effort has been linked to more violence, human-rights abuses, and deaths.

“You saw, literally, cops and soldiers patrolling ... in various neighborhoods in Juarez," and other places, David Shirk, a professor at San Diego University who runs the school's Justice in Mexico program, told Business Insider in late 2015.

"I remember walking the streets of Ciudad Juarez and wondering whether the city of my childhood was dying," Corchado said.

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Ciudad Juarez Chihuahua Mexico crime scene police children victims

REUTERS/Gael Gonzalez

The violence continued falling between 2013 and 2015, driven down by civil-society and citizen-security efforts, but also likely by the triumph of the Sinaloa cartel in its fight with the Juarez cartel for control of the plaza, or trafficking territory, in and around the city.

"What happened was they killed each other," said Gustavo de la Rosa Hickerson, a representative of the Chihuahua State Human Rights Commission during the peak of the cartel fighting. "So many people died ... that part of the reduced violence was because of the extinction of [the cartels'] members, and who survived fled."

2016, however, witnessed an increase in violence many have attributed to drug-trafficking organizations. The brunt of that increase came in the latter half of the year.

"The increase really didn't start this year until about August, so that was after the ... local election, the state and municipal elections, which took place in July, and then the new people take office in October," Molloy told Business Insider.

The timing of the spike led many observers to attribute the outburst of killings to uncertainty generated by the changeover in government.

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Ciudad Juarez Mexico crime cartels violence drug trade

REUTERS/Jose Luis Gonzalez

"In other words, the parties changed at the both state level and the local level after the elections this year," Molloy said.

"So in general the way the system works is the people who are kind of in charge of the major criminal operations in the city, they'll have arrangements with local leadership, both in government and in the police, and then so when the government changes, they have to negotiate some kind of new arrangement," Molloy told Business Insider, describing the way many people viewed the narco-politico relationship.

"It is clear that with the change of government, there also comes a struggle for control among criminal rackets, especially in Juarez and Chihuahua City," Howard Campbell, an anthropologist and expert on national security at the University of Texas at El Paso, told The El Paso Times in August.

"When a new regimen comes, there usually is a 'cleaning of the house' in the criminal world," he said at the time.

Tremors in the government-cartel relationship were not the only drivers, however.

A dispute about the drug trade itself is thought to have spurred on growing conflict between the long-dominant Sinaloa cartel and the remnants of the Juarez cartel that remain active in the city.

"The government, in their statements to the newspapers, starting in August ... was saying that the uptick in violence was due to things happening in the local, domestic methamphetamine trade," Molloy told Business Insider.

"The war is because [the Sinaloa cartel] wants [to sell] the crystal and we aren't going to leave, there are orders to do whatever in order to not permit any of that," Jorge, a mid-level enforcer and recruiter for La Linea, the armed wing of the Juarez cartel, told El Universal late last year.

Mexican authorities in 2016 attributed the spike in violence to disputes over small-scale drug sales, particularly of crystal meth.

"Recently, two human heads were found left in a Juarez neighborhood inside coolers ... along with a narco mensaje," or narco message, Corchado said. "The bodies were found later. The mensaje was, 'this is a warning to anyone who sells crystal meth.'"

'A new dynamic'

Added to the lethal mix in Juarez is the reported arrival of the Jalisco New Generation cartel, or CJNG. Formed around 2010 from a former branch of the Sinaloa cartel in southwest Jalisco state, the eponymous cartel has surged to the top of Mexico's narco hierarchy in recent years.

"In this Juarez-El Paso corridor we are beginning to make confiscations and some arrests linked to the CJNG," Will R. Glaspy, a special agent with the US Drug Enforcement Administration and chief of the El Paso division, told Mexican news magazine Proceso.

"The operations of the CJNG in this zone represent a new dynamic for us," Glaspy said.

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Mexico Ciudad Juarez Chihuahua crime scene homicide killing victim

REUTERS/Jose Luis Gonzalez

"Nueva Generacion and La Linea, aka the Juarez cartel, have formed an alliance to finish off a deeply fragmented Sinaloa cartel and take control of one of the most lucrative routes, the Juarez-El Paso distribution route that supplies chains all over the United States, particularly the southwest, where meth's epidemic is high," Corchado said at the Wilson Center event.

"What is interesting is how the Juarez and Nueva Generacion have like a campaign in the city where they say, 'We're trying to finish off the Sinaloa cartel to try to keep the meth off the streets because the meth is so destructive,'" he added.

Jorge, the enforcer with La Linea, said something similar at the end of 2016.

"The people that use the crystal only last three years and they die. We are killing people [for selling meth] and that money is going to us, because that which they spend on crystal they can use on heroin," he told El Universal.

'Unintended consequences'

Regardless of their sentiments about meth, the cartel competition for Juarez has had clear results.

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Mexico Ciudad Juarez homicides 2016 2017 chart

Mexican government data; El Diario

Through the first six months of 2016, the city saw 166 homicides, according to the Mexican federal government. (Mexican government statistics often understate the number of high-impact crimes like homicides.)

Over that same period, according to Juarez-based newspaper El Diario, there were 192 homicides.

In the latter half of the year, there were 304 homicides, according to government figures, while El Diario recorded 357.

Government data also shows 46 homicides in the city in January, while El Diario reported 54 killings that month and 84 in February, making it the most violent February in the city since 2011.

"The year 2016 marked the worst year in homicides in Ciudad Juarez," Corchado said.

"The level of brutality and style of killings are reminiscent of that that was seen between 2008 and 2012 between the Juarez and Sinaloa cartels."

Many of those killings came in execution-style or drive-by shootings. In late October, a series of multi-person homicides stirred memories of the worst of Juarez's violence a half-decade ago.

The spike in killings through 2016 came as Joaquin "El Chapo" Guzman — vaunted kingpin of the powerful Sinaloa cartel — languished in jail after his recapture in January, spending much of that time in a prison just outside Juarez.

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Joaquin El Chapo Guzman Mexico extradition jail Sinaloa cartel

Mexico's Attorney General's Office/Handout via REUTERS

Guzman was extradited to the US in January, whisked away from Juarez to a jail in New York City in the waning hours of Barack Obama's term. (It's not clear why it was timed that way, though Mexicans appear to be unhappy with the transfer.)